A ray of light is incident on the surfaces of a spherical glass paper- weight making an angle a with the normal and is refracted in the medium at an angle B. calculate the deviation.

A ray of light is incident on the surfaces of a spherical glass paper-

1.	A ray of light is incident on the surfaces of a spherical glass paper- weight making an angle a with the normal and is refracted in the medium at an angle B. calculate the deviation.
Answer» SOLUTION :Deviationn MEANS the angle through while the incident ray is turned in emerging from the medium. In figure if AB and DE are the incident and emergent rays respectively, the deviation will be `DELTA.` Now as at B `ANGLEI= angle a and angler= B` So from Snell.s law `I sin a= mu sin B`........(1) Now from geometry of figure at D, `anglei= beta` So `mu sin beta= 1 sin gamma` Comparing Eqs. (1) and (2) `gamma = alpha` Now as in a triangle exterior angle is the sum of remaining two interior angles in `Delta ABCD`, `delta (a-B)+(a-B)=2(a-B)`